1. Field of the Invention
The present invention relates to an image input device using a linear sensor for example, a solid-state image sensing device and a driving method thereof.
2. Description of the Background Art
As a linear sensor, a CCD linear sensor 1 according to an offset-site pick-up method as shown in FIG. 15A, for example, has been developed. The CCD linear sensor 1 includes a first sensor array (so-called main sensor array) 3 and a second sensor array (so-called sub sensor array) 4, both having a plurality of sensor portions 2 to be pixels arranged in one direction. On respective one sides of the sensor arrays 3 and 4, a first transfer register (so-called main transfer register) 7 and a second transfer register (so-called sub transfer register) 8 in a two-phase driven CCD structure, for example, are provided through reading gate portions 5 and 6, respectively.
The two sensor arrays 3 and 4 are formed shifted by half a pitch from one another, and, as shown in FIG. 15B, the distance X1 between the sensor arrays 3 and 4 is an integral multiple of the pixel pitch X2 (X1=nX2 where n=integer). This is for the purpose of raising the MTF (Modulation Transfer Function).
The first and second transfer registers 7 and 8 are connected to a common transfer register portion 9 in a CCD structure to be coupled on the output portion side. Next to the final stage of the common transfer register portion 9, an output gate portion 10, and a floating diffusion region 11, for example, to serve as a charge-voltage conversion portion are provided. A reset gate portion 12 and a reset drain 13 are formed adjacent to the floating diffusion region 11. The floating diffusion region 11 is connected with an output circuit 14.
In the CCD linear sensor 1, when the maximum resolution is necessary, signal charges in the first sensor array (main sensor array) 3 and the second sensor array (sub sensor array) 4 are read out to the transfer registers 7 and 8, respectively, for transfer therein, and the signals from the first and second sensor arrays 3 and 4 are alternately outputted through the common transfer register portion 9, the floating diffusion region 11 and the output circuit 14. Then, the temporal difference between the positions of sensor portions 2 in the first sensor array 3 and sensor portions 2 in the second sensor array 4 is corrected at a signal processing portion for forming an image.
Meanwhile, when only xc2xd the maximum resolution is necessary for an image, signal charges in the second sensor array 4 are not necessary, and only signal charges in the first sensor array 3 are processed and outputted. In this case, the unnecessary signal charges in the second sensor array 4 are swept away to the reset drain 14 through the reset gate portion 12 via the floating diffusion region 11.
FIG. 16 shows another CCD linear sensor 16 having a different layout from the sensor array in FIGS. 15A and 15B. The CCD linear sensor 16 has a first sensor array (so-called main sensor array) 3 and a second sensor array (so-called sub sensor array) 4, both having a plurality of sensor portions 2 to be pixels arranged in one direction similarly to the above example. On respective one sides of the sensor arrays 3 and 4, a first transfer register (so-called main transfer register) 7 and a second transfer register (so-called sub transfer register) 8 in a two-phase driven CCD structure for example are provided through reading gate portions 5 and 6, respectively.
In the CCD linear sensor 16, the sensor arrays 3 and 4 are provided on the same side of the transfer registers 7 and 8, respectively. In the sensor arrays 3 and 4, before and after the regular sensor portions 2 (S1 to Sn) and 2 (S1xe2x80x3 to Snxe2x80x3) to generate signal charges to form image signals, dummy sensor portions 2 (D1xe2x80x3 to Dnxe2x80x3) and 2 (Dn+1xe2x80x3 to Dm) and dummy sensor portions 2 (D1xe2x80x3 to Dnxe2x80x3) and 2 (Dn+1xe2x80x3 to Dm) to obtain the black reference level of an output signal are provided. The dummy sensor portions 2 (D1 to Dn), 2 (D1xe2x80x3 to Dnxe2x80x3) and 2 (Dn+1 to Dm), 2 (Dn+1xe2x80x3 to Dnxe2x80x3) have their upper surfaces covered with a light shielding film.
The dummy sensor portions are provided in the sensor arrays 3 and 4 in FIGS. 15A and 15B as described above.
In addition, similarly to the description in connection with FIGS. 15A and 15B, the first and second transfer registers 7 and 8 are connected to the common transfer register portion 9 in the CCD structure so as to be coupled on the output portion side. Next to the terminal end of the common transfer register portion 9, an output gate portion 10, and a floating diffusion region 11, for example, to be a charge-voltage conversion portion are formed. A reset gate portion 12 and a reset drain 13 are formed adjacent to the floating diffusion region 11. The floating diffusion region 11 is connected with the output circuit 14.
The CCD linear sensor 16 is driven similarly to the CCD linear sensor 1 shown in FIGS. 15A and 15B, as described above, and when a high resolution is necessary, signal charges in the first sensor array (main sensor array) 3 and second sensor array (sub sensor array) 4 are read out and processed to form a high resolution image. If a high resolution is not necessary, signal charges in the second sensor array 4 are not necessary, and only signal charges in the first sensor array 3 are processed for output.
In the CCD linear sensors 1 and 16, when only signal charges in the first sensor array (main sensor array) 3 are outputted, signal charges generated at the second sensor array (sub sensor array) 4 are swept away to the reset drain 13. Therefore, the signal charges must be transferred to the floating diffusion region 11, and the signals in the first sensor array 3 could be affected by the unnecessary signals in the second sensor array 4.
This is because the signals in the first sensor array 3 and the second sensor array 4 are alternately outputted and subjected to coupling at the output buffer portion (so-called output circuit portion 14). In particular, if the first sensor array 3 is in a black state, and the spatially separated second sensor array 4 changes from black to white, the signal in the first sensor array 3 subtly changes.
When a reading is performed at a high speed and a high resolution is not necessary, the frequency of a transfer clock pulse must be high, and therefore the data region is shortened, which makes signal processing at the outside difficult.
In a CCD linear sensor in which signal charges of the pixels (sensor portions) in a sensor array are allocated to a plurality of CCD transfer registers and read out, when pixels are thinned and only the signal charges of desired pixels are read out, the signal charges of the selected pixels are affected by the signal charges of the other pixels.
Meanwhile, in a CCD linear sensor such as color CCD linear sensor having a plurality of sensor arrays, if there is a reading mode to selectively read out only signal charges in a prescribed sensor array other than reading out the signal charges in all the sensor arrays, the signal charges in a non-selected array or the charges of a smear component are preferably easily swept away.
The present invention relates to the above point, and it is an object of the present invention to provide an image input device, a solid-state image sensing device, and a driving method thereof which allow selected signal charges to be unaffected by unnecessary signal charges in a non-selected transfer register or allow the unnecessary signal charges to be easily swept away at the time of reading out signal charges in a desired sensor array or desired sensor portions using a plurality of selected transfer registers, or allow high speed reading when a high resolution is not required.
The image input device according to the present invention has two or more reading modes in which signal charges in a desired sensor array or desired sensor portions can be read out using a plurality of selected transfer registers, and a transfer register not selected is provided with charge sweep means for sweeping away unnecessary charges.
In the image input device according to the present invention, with these two or more reading modes, signal charges in a desired sensor array or desired sensor portions may be selectively read out as required. Since the not-selected transfer register is provided with the charge sweep means, unnecessary charges at the non-selected transfer register (non-selected signal charges or/and charges of a smear component) are not transferred the to charge-voltage conversion portion but are swept away through the charge sweep means. Therefore, the selected signal charges are not affected by unnecessary charges.
When only signal charges in a desired sensor array or desired sensor portions are read out, high speed reading is enabled at the same driving frequency as compared to the mode of reading out all the sensor arrays or all the sensor portions, while for the same reading time, signal processing at the outside is easier for the amount reduced in the driving frequency.
The solid-state image sensing device according to the present invention has a sensor array and a plurality of transfer registers. A transfer register not selected depending upon a reading mode is provided with charge sweep means for sweeping away unnecessary charges.
In the solid-state image sensing device, the charge sweep means is provided to a plurality of transfer registers or a transfer register not selected depending upon the reading mode, and therefore unnecessary charges (non-selected signal charges or/and charges of a smear component) at the non-selected transfer register are not transferred to a charge-voltage conversion portion but are swept away through the charge sweep means. As a result, the selected signals are not affected by the unnecessary charges.
When only signal charges in a desired sensor array or desired sensor portions are read out, high speed reading is enabled at the same driving frequency as compared to the mode of reading out all the sensor arrays or all the sensor portions, while for the same reading time, signal processing at the outside is easier for the amount reduced in the driving frequency.
By a method of driving a solid-state image sensing device according to the present invention, when signal charges in a desired sensor array or desired sensor portions are read out using a plurality of selected transfer registers, unnecessary charges at a non-selected transfer register are not transferred to a charge-voltage conversion portion but are swept away.
By the driving method according to the present invention, when signal charges in a desired sensor array or desired sensor portions are selectively read out, unnecessary charges at a non-selected transfer register (non-selected signal charges or/and charges of a smear component) are not transferred to the charge-voltage conversion portion, but are swept away. Therefore, the selected signal charges are not affected by the unnecessary charges.
When only signal charges in a desired sensor array or desired sensor portions are read out, high speed reading is enabled at the same driving frequency as compared to the mode of reading out all the sensor arrays or all the sensor portions, while for the same reading time, signal processing at the outside is easier for the amount reduced in the driving frequency.
The solid-state image sensing device according to the present invention includes a plurality of sensor arrays, a plurality of transfer registers, and charge sweep means provided at each sensor array or a prescribed sensor array. The device further includes charge sweep means for sweeping away charges in a non-selected sensor array when signal charges in a desired sensor array are read out, and means for selectively turning off the reading gate portion of the non-selected sensor array.
In the solid-state image sensing device according to the present invention, when signal charges in a desired sensor array are read out, the charge sweep means for the non-selected sensor array is selected and attains a charge sweeping state. Meanwhile, the reading gate portion of the non-selected sensor array is selected and turned off. Thus, the signal charges in the non-selected sensor array are not read out to the transfer register, but are swept away to the charge sweep means. As a result, signals in the selected sensor array may be read out at a high speed without being affected by the signals in the non-selected sensor array.
When only signal charges in a desired sensor array are read out, high speed reading is enabled at the same driving frequency as compared to the mode of reading out all the sensor arrays, while for the same reading time, signal processing at the outside is easier for the reduced amount in the driving frequency.
By a method of driving a solid-state image sensing device according to the present invention, at the time of reading out signal charges in a desired sensor array among a plurality of sensor arrays, signal charges in a non-selected sensor array are not read out to the transfer register but are swept away.
By the driving method according to the present invention, signal charges in the non-selected sensor array are not read out to the transfer register but are swept away, so that signals in a selected, desired sensor array may be read out at a high speed without being affected by the signals in the non-selected sensor array.
When only signal charges in a desired sensor array are read out, high speed reading is enabled at the same driving frequency as compared to the mode of reading out all the sensor arrays or all the sensor portions, while for the same reading time, signal processing at the outside is easier for the amount reduced in the driving frequency.